The subject matter described herein relates generally to methods and systems for wind turbines, and more particularly, to methods and systems for braking or locking of wind turbines.
At least some known wind turbines include a tower and a nacelle mounted on the tower. A rotor is rotatably mounted to the nacelle and is coupled to a generator by a shaft. A plurality of blades extend from the rotor. The blades are oriented such that wind passing over the blades turns the rotor and rotates the shaft, thereby driving the generator to generate electricity.
Some known wind turbines include a rotor-brake and a rotor-lock. The rotor-lock typically provides a higher load limit, especially when the brake is applied at the low-speed shaft of the turbine. The load limit of the rotor-lock is designed for a maximum expected load, e.g. during a storm. The rotor-lock may only be applied when the rotor shaft of the wind turbine stands still. The rotor-brake typically provides a lower load limit, wherein higher loads do not lead to a damage of the rotor-brake. The rotor-brake provides slip if the load gets higher than the load limit of the rotor-brake. Rotor-brakes may sometimes also be used when the rotor shaft is rotating slowly to stop the rotor shaft completely. Technical background to rotor-brakes and rotor-locks, or other methods for applying a braking force to a rotor shaft of a wind turbine, may be found in U.S. Pat. No. 7,948,100.
The costs for the rotor-brake and the rotor-lock of a wind turbine contribute to the total costs of the wind turbine with several percent. There is therefore a need for a method and a wind turbine using the rotor-brake and the rotor-lock more efficient to maybe reduce the size and costs of the rotor-brake or the rotor-lock.